Well, just to add my 2 cents, it is certainly possible to get 100+ AAs before 65 as a tank. It takes some work yes, and is very frustrating. I was a "casual play" Shadow Knight and didn't even join a raid guild till level 70 with 250+ AAs. I felt the tank curse of not being able to tank in the high end game without the AAs and gear, but I am telling you...despite all the pain and suffering, it is all well worth it.
No, I could not solo past 61 (this was before the days of the new fear spells) so don't give me that SK can solo phooey. I tanked in groups from 62-70 with about 20 AAs at level 61 to start. By 65, I had about 120 AAs before I went to 70. And yes, people gave me a lot of crap, people would not group with me, and I could not tank anything past LDoN, Sebilious or Droga for a long while, where the xp sucks. I was referred to as a 'suck' tank...judged by my low hps.
But, despite all the bull, I fought through it, got better gear through LDoN, to OoW, to Cultural...and now, I DON'T EVEN PUT MY LFG TAG UP. All I have to do is log in and be unanon for about 5 minutes, and people start sending me tells. With the tank curse above, comes a shortage of tanks that can tank MPG, the Nest, GOD,RSS, and pretty much all the new expansion..so all you got to do is make it over the hump, then the groups will come to you. You will develop a reputation, and they will seek you out. Your reputation is gold. Then YOU can be picky if you so choose.
I am telling you tanks, if you suck, except it, work on it..if someone gives you a tell to come tank MPG, be honest and tell them "sorry, I can't tank that yet". WORK THOSE AAs...get all the Defensive/HP/Mitigation/Avoidance AAs pre-OoW to start, then work up from there (this is probably about 100 or so AAs, which makes that guys estimate above pretty right on). I am telling you, it is certainly possible without a raid guild and without sacrificing your real-life. I didn't believe it myself...I was even a whiner too. But...I am on the other side now, and the grass DOES taste sweeter
Finally, don't shun druids as healers. In my experience, they make damn fine healers sub MPG...and the ones I played with didn't have a lot of AAs either. Sure cleric is ideal, but if there is none to group with you cause you suck, hook up with a druid....they are just as desperate for xp as you probably.